The present invention relates to a structure comprised of aluminum alloy and to a railway car comprised of aluminum alloy; and, in particular, the invention relates to a structure, such as a body of a railway car, an automobile, a ship, an air plane, an elevator and a pressure vessel, and to the construction of a railway car.
A technique for friction stir welding is disclosed in Japanese application patent announcement laid-open publication No. Hei 7-505090, in which a rotary tool made of a material which is substantially harder than a member to be subjected to processing is inserted into a welding portion of two members to be subjected to processing, and the rotary tool is rotated and moved along a welding line, whereby it is possible to carry out a continuous friction stir welding along the welding line direction of the members to be subjected to processing.
Namely, this friction stir welding method involves a welding technique which utilizes the plastic fluidity of a metal fluidized in friction heat which is generated between the rotary tool and the member to be subjected to processing, whereby friction stir welding can be carried out (hereinafter, a friction stir welding method). Such a friction stir welding method has a characteristic in which, in comparison with fusion welding, such as arc welding, a solid phase welding is carried out wherein it is possible to weld without a fusion phenomenon. Accordingly, in the above stated friction stir welding method, since the heating temperature is low, there are many advantages, including the fact that the deformation of the member to be subjected to processing after the friction stir welding is small etc.
On the other hand, up to now, a railway car has been manufactured using an aluminum alloy. The aluminum alloy members of the railway car were fusion-welded using an arc welding method, and then the fusion welded members were assembled as a railway car. However, according to conventional arc welding characteristics, the deformation of the member to be subjected to processing by the arc welding is large, and repair of such deformation of the member to be subjected to processing requires necessarily much working time.
Herein, for the welding of a railway car when the above-stated friction stir welding method is employed, effects are attained in which the welding deformation of the member to be subjected to processing is small, and the welding of the front and the rear faces can be carried out because solid phase welding is carried out.
The above-stated friction stir welding utilizes the plastic fluidity produced by the friction heat generated between the rotary tool and a welding member to be subjected to processing. Accordingly, the friction stir welding characteristic differs largely for different kinds of aluminum alloys. As the aluminum alloy having a superior friction stir welding characteristic, it is desirable to employ an alloy having a superior plastic fluidity created by the friction heat between the rotary tool and the member to be subjected to processing.
However, all aluminum alloys do not necessarily have such a superior plastic fluidity. In the case of an aluminum alloy having an inferior plastic fluidity, a large resistance is present between the rotary tool and the welding member to be subjected to processing. Accordingly, the wear and tear on the rotary tool is large and the life time of the rotary tool becomes short.
In particular, in the case of railway car manufacturing, since the welding length is as long as 25 m as a maximum, when the wear and tear on the rotary tool is large, there is a large possibility that a welding defect will occur during the welding operation. As a result, when the welding member to be subjected to processing is long, it is impossible to continuously carry out the friction stir welding. Further, a large resistance is imposed on the welding member to be subjected to processing. Accordingly, it is necessary to make the welding member large in size, particularly in the thickness direction of the welding member to be subjected to processing.
However, when the size of the welding member to be subjected to processing is made large, since the railway car weight increases, it is not desirable from the point of view of high speed operation of the railway car. Further, in a case where the resistance of the rotary tool is large, the clamp force for fixing the welding member to be subjected to processing becomes large. Accordingly, the clamp tool size becomes large, causing problems concerning fixing of the welding member to be subjected to processing and the working performance.
On the other hand, in the above-stated friction stir welding method, since a surface of the welding portion of the welding member to be subjected to processing is cut off by the rotary tool, causing the surface of the welding portion of the welding member to be subjected to processing to have a recessed portion (a dent portion or a sink portion), a problem is created from the aspect of reliability of performance.
Further, in a conventional welding joint structure, metal, which has been subjected to plastic fluidity by the friction heat generated between the rotary tool and the welding member to be subjected to processing, flows from a groove portion, causing a problem in which a welding defect can be generated at the welding portion of the welding member to be subjected to processing.
An object of the present invention is to provide a structure comprised of an aluminum alloy having a low welding distortion and to provide a railway car comprised of an aluminum alloy having a low welding distortion.
According to the present invention, in a railway car, extruded frame members of an aluminum base alloy containing Si of 0.4-0.9 wt % and Mg of 0.4-1.2 wt % are welded using friction stir welding.
In a structure, an aluminum base alloy plate containing Si of 0.4-0.9 wt % and Mg of 0.4-1.2 wt % is prepared, and to one face of the aluminum base alloy plate a rib is formed, wherein the aluminum base alloy plate is an extruded frame member.
In a structure, two aluminum base alloy plates containing Si of 0.4-0.9 wt % and Mg of 0.4-1.2 wt % are prepared, and the two aluminum base alloy plates are formed integrally by a rib, wherein the respective aluminum base alloy plates are extruded frame members.
In a railway car, a welding portion of the extruded frame members is welded under a condition wherein the extruded frame members overlap each other.
In a railway car, a surface of a welding portion of the extruded frame member has a projection of a height of 0.5-3 mm.
In a structure, at an end portion of a face of the aluminum base alloy plate, a rib is provided vertically relative to the aluminum base alloy plate.
In a structure, at an outer face side of end portions of the two aluminum base alloy plates, a projection is provided.
In a structure comprising aluminum base alloy members containing Si of 0.4-0.9 wt % and Mg of 0.4-1.2 wt % which are welded at a welding portion using friction stir welding, to a welding side surface of the welding portion, a projection is provided before the friction stir welding is carried out.
In a method of manufacturing a structure in which aluminum base alloy members containing Si of 0.4-0.9 wt % and Mg of 0.4-1.2 wt % are welded, using a rotary tool by friction stir welding, to a welding side surface of a welding portion, a projection is provided, the rotary tool is inserted from a side of the projection, and then the friction stir welding is carried out.
The above-stated aluminum alloy is manufactured by an extrusion processing, and, after the processing, the aluminum alloy is subjected to a solution thermal processing and an aging (hardening) thermal processing.
The above-stated aluminum alloy is manufactured by an extrusion processing and a solution thermal processing at the same time, and after those processings, an aging (hardening) thermal processing is carried out.
A surface of a friction stir welding portion of the member to be subjected to processing, comprised of the above-stated aluminum alloy, is as high as 0.5-3 mm before the friction stir welding.
A part of the friction stir welding portion of the member to be subjected to processing, comprised of the above-stated aluminum alloy, is friction stir welded to the other member under a condition where the members overlap each other.
A car of a railway vehicle is manufactured by an extrusion processing of a member to be subjected to processing, comprised of the aluminum alloy, having a long size which is a maximum 26 m. Accordingly, it is necessary for the member to be made of an aluminum alloy having a superior extrusion processing performance.
Further, a railway car is required to have a superior mechanical strength. Thus, to lessen the welding distortion produced during welding and further to manufacture with a high reliability, in place of the conventional fusion welding, it is desirable to employ a friction stir welding method to which a solid phase welding is carried out.
As an aluminum alloy having a superior friction stir welding performance, it is desirable to carry out the aging (hardening) thermal processing, after the solution thermal processing of an aluminum alloy in which the Si content of 0.4-0.9 wt % and Mg content of 0.4-1.2 wt % are comprised as a main composition. In other words, as stated above, in a case where the railway car body comprised of an aluminum alloy is assembled by the friction stir welding method, it is desirable to use an aluminum alloy having a superior friction stir welding performance, a superior extrusion processing performance and a superior mechanical strength performance. As a result, according to the present invention, since an aluminum alloy having a superior friction stir welding performance, a superior extrusion processing performance and a superior mechanical strength performance is assembled in accordance with the above-stated friction stir welding method, then a railway car having the desired characteristics and advantages can be manufactured.
On the other hand, the appearance of a recessed portion (a dent portion) on the surface of the welding portion of the member to be subjected to processing due to the cut-off (the deletion) of the rotary tool is prevented by a method in which the welding portion of the member to be subjected to processing is provided with an area of increased height in advance. As to the height (H) of the welding portion of the member to be subjected to processing, the effect is small when a height (H) of less than 0.6 mm is employed, however a height (H) of more than 3 mm also is not desirable because the height which remains after the welding is excessive. Accordingly, as the height (H) of the welding portion of the member to be subjected to processing, it is desirable to employ a height of more than 0.6 mm, but less than 3 mm.
Further, an occurrence of a welding defect, produced by flow-out of the plastic fluidized welding metal which exists between the members to be subjected to processing, can be prevented by employing an arrangement in which, in a part of the welding joint portion, the members to be subjected to processing are overlapped on each other.